<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>let</title>
</head>
<body>
    <script>
        //声明变量
        let a;
        let b,c ,d;
        let e=100;
        let f=521,g='you',h=[];
        //1.变量声明不能重复
        // let star='me';
        // let star='you';

       //2. 块儿级作用域  全局, 函数, eval
        // if else while for 
        {
            let girl = '周扬青';
            console.log(girl);
        }
        // console.log(girl);

         //3. 不存在变量提升
        // console.log(song);
        // let song = '恋爱达人';

        //4. 不影响作用域链
        {
            let school = 'ES6';
            function fn(){
                console.log(school);
            }
            fn();
        }
    </script>
</body>
</html>